The shape of the mericarps is very helpful in distinguishing the species of Gouania. The dumbbell-shape mericarps are transversely oblong with a very broad sinus at the apex and base of the fruit body. The fruit body itself is like the narrow bar or handhold of the dumbbell. Bornstein (1989: 165) described this fruit shape as “Fruit wing attached to side of fruit body only,” and I borrow his description. It’s not technically true as a thin margin of the wing continues along the apex and base of the fruit body, but it does help to explain the shape. The other shape I term the butterfly. The butterfly-shape mericarps are more or less circular to transversely oblong with emarginations to deep clefts at the apex and base of the fruit body, or only at the base in G. velutina. Bornstein (1989:165) described this type as “Fruit wing attached to side and base, and/or apex of fruit body” and I borrow again from him. To help define the shape of mericarps, the following measurements were made: height of fruit body, height of mericarp wings, distance between highest points of two wings, width of mericarp, and width of fruit body.

1. Fruits glabrous or with few trichomes over fruit body only (rarely with few trichomes on wings in G. polygama)

2. Fruit mericarp butterfly shaped with emarginations at apex and base, the wings more or less attached to apex and base of fruit body as well as sides, height of fruit body 4—7 mm, the width across the entire mericarp 1.5—3.3 times the height of the fruit body and (rarely, or) distance between highest points of two wings of mericarp 2/3rds to equal height of fruit body; annulus of disc glabrous; pairs of lateral veins (3) 4 or 5 (6); stipules usually retained (at least in part) into fruiting … G. lupuloides

2. Fruit mericarp out-line dumb-bell shaped, the wings more or less attaching to the sides of fruit body only, height of fruit body (2.5--) 3—4 mm, the width across the entire mericarp usually 3—4 (-5) times the height of the fruit body and (rarely, or) distance between highest points of two wings of mericarp usually 2—3 times height of fruit body; annulus of disc pilose; pairs of lateral leaf veins (6) 7 or 8 (9); stipules caducous often before leaves expand… G. polygama

3. Disc glabrous; disc lobes (1/2--) 2/3rds to equal to sepals in length; at least some stipules usually retained into fruit, 2-lobed, the lower lobe more or less orbicular or broadly reniform, 3.5—10 x 4—11 mm; mature mericarp out-line butterfly shaped with emargination at base only and the apex truncate or nearly so; expected in southwestern Nicaragua … G. velutina

3. Disc (excluding, or often including, lobes) entirely covered with trichomes, or trichomes around annulus and extending in numerous rays from annulus onto disc (rarely only around annulus in G. hypoglauca); disc lobes 1/6—1/3 length of sepals; stipules usually caducous, un-lobed or lower lobe a very small foot, if present, 0.2—1 x 0.1—0.5 mm; mature mericarps butterfly shaped with emarginations at apex and base